UK National Insurance Calculator - Contribution Estimate

The UK National Insurance calculator estimates contributions from earnings for the 2024–25 tax year. Select employment type, National Insurance class, weekly, monthly, or annual earnings, and the tax year. It annualizes the earnings, calculates the applicable contribution, then converts that estimate back to the selected earnings period. The output also displays a Class 1 employee estimate and an employer estimate for comparison. It can help employees, self-employed workers, and payroll planners understand the broad effect of NI thresholds before checking payslips or official guidance. For Class 1 employees, the calculator applies 8% to annual earnings between £12,570 and £50,270, then 2% to earnings above £50,270. The employer comparison applies 13.8% to earnings above £9,100. For the combined self-employed Class 2 and Class 4 option, it applies the 2024–25 Class 4 rates: 6% on profits between £12,570 and £50,270 and 2% above that level; it does not add a mandatory Class 2 charge. The voluntary Class 3 option uses the annualized weekly voluntary rate. Weekly earnings are multiplied by 52 and monthly earnings by 12 before the annual calculation. This makes the thresholds comparable across input periods, but it is an estimate rather than a payroll engine. The chosen class determines the main annual contribution shown. The separately displayed employee and employer figures are particularly useful for a Class 1 employment example; they are not a statement of employer cost for self-employment or voluntary contributions. Currency is fixed to pounds sterling because the statutory thresholds are UK values. National Insurance rules, thresholds, and rates can change between tax years, and payroll may include category letters, pay-period thresholds, director rules, deferment, benefits, or rounding conventions not modeled here. Use this calculator for a clear planning estimate, then confirm an important result with GOV.UK guidance, payroll software, or a qualified adviser. Do not use it as a substitute for a payslip calculation or tax return.